Seventy six T dwarfs from the UKIDSS LAS: benchmarks, kinematics and an updated space density
Abstract
We report the discovery of 76 new T dwarfs from the UKIDSS Large Area Survey (LAS). Near-infrared broad and narrow-band photometry and spectroscopy are presented for the new objects, along with WISE and warm-Spitzer photometry. Proper motions for 128 UKIDSS T dwarfs are presented from a new two epoch LAS proper motion catalogue. We use these motions to identify two new benchmark systems: LHS 6176AB, a T8+M4 pair and HD118865AB, a T5.5+F8 pair. Using age constraints from the primaries and evolutionary models to constrain the radii we have estimated their physical properties from their bolometric luminosity. We compare the colours and properties of known benchmark T dwarfs to the latest model atmospheres and draw two principal conclusions. Firstly, it appears that the H - [4.5] and J - W2 colours are more sensitive to metallicity than has previously been recognised, such that differences in metallicity may dominate over differences in Teff when considering relative properties of cool objects using these colours. Secondly, the previously noted apparent dominance of young objects in the late-T dwarf sample is no longer apparent when using the new model grids and the expanded sample of late-T dwarfs and benchmarks. This is supported by the apparently similar distribution of late-T dwarfs and earlier-type T dwarfs on reduced proper motion diagrams that we present. Finally, we present updated space densities for the late-T dwarfs, and compare our values to simulation predictions and those from WISE.
Keywords
Cite
@article{arxiv.1304.7246,
title = {Seventy six T dwarfs from the UKIDSS LAS: benchmarks, kinematics and an updated space density},
author = {Ben Burningham and C. V. Cardoso and L. Smith and S. K. Leggett and R. L. Smart and A. W. Mann and S. Dhital and P. W. Lucas and C. G. Tinney and D. J. Pinfield and Z. Zhang and C. Morley and D. Saumon and K. Aller and S. P. Littlefair and D. Homeier and N. Lodieu and N. Deacon and M. S. Marley and L. van Spaandonk and D. Baker and F. Allard and A. H. Andrei and J. Canty and J. Clarke and A. C. Day-Jones and T. Dupuy and J. J. Fortney and J. Gomes and M. Ishii and H. R. A. Jones and M. Liu and A. Magazzu and F. Marocco and D. N. Murray and B. Rojas-Ayala and M. Tamura},
journal= {arXiv preprint arXiv:1304.7246},
year = {2015}
}
Comments
MNRAS accepted. Updated 9th May 2013 to correct error in column headings for Table 4